CPT® Code 85270

The CPT® Code 85270 refers to a laboratory test that measures the activity of clotting factor XI, which is also known as plasma thromboplastin antecedent (PTA). This test is crucial for diagnosing conditions related to clotting deficiencies, particularly hemophilia C and Rosenthal syndrome, both of which are associated with a deficiency in factor XI. Factor XI plays a significant role in the coagulation cascade, functioning as a zymogen that is activated by factor XIIa or thrombin. Once activated, it acts as a trypsin-like serine protease, facilitating the activation of other clotting factors and enzymes necessary for proper blood coagulation. Factor XI exists in two forms within the body: platelet factor XI, which is produced by megakaryocytes, and plasma factor XI, synthesized in the liver. A deficiency in factor XI is primarily inherited and affects both males and females equally. However, it can also occur, albeit rarely, in patients with lupus erythematosus. The clinical manifestations of factor XI deficiency can vary significantly among individuals and do not always correlate with the measurable levels of factor XI in the blood. Some patients may experience immediate or delayed bleeding episodes, while others may report heavy menstrual bleeding, particularly among women. Interestingly, many individuals with factor XI deficiency may not exhibit any bleeding symptoms at all, and the condition is often identified through abnormal laboratory tests, such as an activated partial thromboplastin time (aPTT) test. The test for factor XI deficiency involves obtaining a blood sample through venipuncture, and the analysis is performed on platelet-poor plasma using an activated partial thromboplastin clot-based assay.